Woa, woa. This is not my experience, Optis are variable consumption engines, anything down to 30:1 according to the dealers, or Barrus themselves. It is entirely dependant on the revs and load apparantly. I know this cos my 150 was drinking it at one point and I got worried, and no it wasn't stuck on running in cycle. But there was no problem, except that the right stuff cost £30 or so a pop (as I remember)